Are two sleeping bags better than one?

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Chris G

Settler
Mar 23, 2007
912
0
Cheshire
Hi folks, Time for a general discussion thread. And the question is; When it's going to be really cold, are two sleeping bags better than one (ie one inside the other as per the US sleeping system)?

Chris
 

shogun

Need to contact Admin...
Mar 31, 2009
747
0
U.K
hi there i bought the snugpak sleep system 2 bags..one for summer use and one for winter use..i have only used the larger bag ov the 2 and i was to warm so i would guess for me the 2 bags together would be 2 warm for me..so i am going to try out the larger bag again as its colder now...soryy i cant be anymore help but i would think the 2 bags would be better atb Allan
 

gregorach

Bushcrafter (boy, I've got a lot to say!)
Sep 15, 2005
3,723
26
47
Edinburgh
I'd argue yes, but not necessarily on the strict terms I think you're implying... There's no reason why you can't make a single bag with the same insulating capacity as two other bags, but the two-bag system has a big advantage in terms of flexibility. I have a 1-2 season down bag which is great when it's not too cold, and a 3-season synthetic bag which I use when it gets too cold. Now, I don't go out in winter any more, but I could put those two together for to produce pretty good 4-5 season setup - so I get 3 different setups (suitable for anything from balmy summer to sub-arctic winter) but from only 2 bags instead of 3.
 

ged

Bushcrafter (boy, I've got a lot to say!)
Yes. And as an alternative to a second sleeping bag, I'd recommend a Goretex or similar bivi bag. I very rarely need any extra warmth than what's provided by my sleeping bag, and I'd usually be too hot if I added another one outside it. But it does tend to collect quite a bit of moisture on its outside in cooler, damper weather. A thin bivi bag fixes that without adding too much extra insulation.
 

Graham_S

Squirrely!
Feb 27, 2005
3,991
20
46
Saudi Arabia
I have the Nanok 0 and -10 which are designed to nest.
I like the concept because it gives great flexibility.
It is important, however, that the outer bag is bigger than the inner one.
If the outer bag is compressing the inner bag, preventing it from lofting, you lose much of the insulation value.
 

Chris G

Settler
Mar 23, 2007
912
0
Cheshire
Well I've dug out my old 2 season bag tonight with a view to using it inside the larger 3 season bag (and a bivi bag) this weekend when they are forecasting that it will be down to minus 10 on Saturday. I've been in the 2 season bag in minus 17 before now and frankly it was unpleasant, so hopefully I'll be toasty this weekend. :)

Chris
 

Mastino

Settler
Mar 8, 2006
651
1
57
Netherlands
I have the Wiggy FTRSS (or something like that) system, with two nesting bags. Gives me warmth & flexibility plus a feeling of backup..
I would say yes for the nesting bags; interestingly: what about a down bag within a synthetic one? Anyone has some experience with that?
 

forestwalker

Bushcrafter (boy, I've got a lot to say!)
I would say yes for the nesting bags; interestingly: what about a down bag within a synthetic one? Anyone has some experience with that?
I did that for a while for winter bags; one 0 C down bag inside a -10 C synthetic fill bag. Warm in -35 C. But, and a very big but, once you are dealing with two sleeeping bags and one bivy (to keep the snow and sparks away) you are dealing with one more zipper, have one more bag that can (will) twist and turn during the night and when you place it inside the other.

It was quite nice, but fighting the combination system in the dark, in a snow trench, when dog tired was not my idea of fun. So I got a Carithia Survival One, which should eventually be replaced with either a new one or the Woodlore equivalent (I fell in love with a center zip)
 
Jan 28, 2010
284
0
ontario
Well I tried that stunt one time when I was moose hunting in Northern Ontario...one bag inside the other...dear lord...woke up
just sweating to death...found much better results by putting the secong bag over me opened up and used like a blanket.
In a perfect world where money is no object I would recommend having a collection of 3 or 4 different bags suited specifically
to the expected conditions. I spend dozens of nights a year in sleeping bags and I find you can get toughened to being a bit
cold at night, but too hot is never comfortable.
 

gregorach

Bushcrafter (boy, I've got a lot to say!)
Sep 15, 2005
3,723
26
47
Edinburgh
interestingly: what about a down bag within a synthetic one? Anyone has some experience with that?
Works fine, subject to the usual caveats about keeping your down bag properly dry and aired. If it's not cold enough, you'll sweat too much and knacker the loft of the down.
 

gregorach

Bushcrafter (boy, I've got a lot to say!)
Sep 15, 2005
3,723
26
47
Edinburgh
If you have the choice, then yeah, probably. But my down bag is very minimalist (no zip) and snug, whereas my synthetic bag has both a zip and quite a bit more space inside it.
 

Paul_B

Bushcrafter (boy, I've got a lot to say!)
Jul 14, 2008
4,553
639
Lancashire
I have a Marmot fusion bag. It has primaloft on the outer layr of insulation and down inside where it can loft around your body. Very effective.

I also have a golite quilt which in colder conditions I could use around this bag.

The one caveat with trying to extend use into winter by layering anything, whether second bag or extra clothing inside your bag, is the effect of reducing the loft of your existing bag. There are systems designed with an overbag made larger than the inner bag. This is good but using two similarly sized bags could end up with the insulation being compressed and not working as efficiently. If you have a snug down bag for instance wearing a down smock on inside it or even any other bulky set of clothing could squah the down from the inside. The effect is you feel colder than without the extra clothing on. IIRC Rab do an effective over bag as do PHD. You could also get one of the XL bags some manufacturers make to put over a standard or small size bag. This could work but I reckon it will still compress the insulation somewhat as XL bag inners are smaller than fully lofted standard bags.

Don't forget to upgrade your mat too if ground dwelling as that can have the effect of 1 season just by getting an Exped downmat for example instead of using a 3 season self inflating mat even with a CCF underneath. It is not for a reason those downmat 7s are rated to -24C!!
 

walker

Full Member
Oct 27, 2006
454
0
50
devon
wont it mean more baggage
i think there only used by military units as a way of trying to give the person a full 4 season choice
or maybe its cheaper for them to run them up like that rather than a full on winter and a seperate summer
i have a airlock -5 which is down and manmade fibre its great very warm light and small
 

W0lf

Tenderfoot
Apr 27, 2009
65
0
London
I have two Snugpak Elite 3 bags which I didn't buy to be used together. However I started thinking about my winter setup and the Elite 3s have a nice in-built extender panel system (EPS) which gives each bag more room. Using this EPS you can join the bags together so they don't twist. You end up with an outer zip and a separate inner zip and this actually works out quite nice as you can regulate the temp by using only one zip or both zips. Given it's only a little bit more weight I really can't justify getting any other bags now. Perhaps I'll post some photos of the EPS and how they join together is you're interested? Whether they are warmer than a large bag with the same volume filling? Probably not but certainly more flexible!